Still it skips over weirdness like the same person being both a sovereign king and vassal of another king. See for example King Henry II of England and Duke of Normandy etc.

Those are the titles bestowed upon him by the UK. But here is the full titles given to him by all entities (including Canada)

https://en.wikipedia.org/wiki/List_of_titles_and_honours_of_...

In Masai he's known as "The Helper of the Cows" (literally: he whom the cows love so much they call for him when they are in times of distress)

Yep, it's absolutely true.

Reference: https://www.canada.ca/en/canadian-heritage/services/crown-ca...

""" Queen Elizabeth II was the first of Canada's sovereigns to be proclaimed separately as Queen of Canada in 1953, when a Canadian law, the Royal Style and Titles Act, formally conferred upon her the title of "Queen of Canada". The proclamation reaffirmed the monarch’s role in Canada as independent of the monarch’s role in the United Kingdom and other Commonwealth realms. """

The other realms the British King has are the Crown dependencies, eg Isle of Man. Australia is the odd one out in naming the UK as one of the other realms. Your head canon was true, before the independence of the Commonwealth countries.

Elizabeth II was at war with herself, briefly.

Jamaica has the monarchy. Jamaican forces were part of the US-led coalition that invaded Grenada in 1983, after the communists seized power. The communists found it politically expedient to maintain the structure of parliamentary government, and so the head of state of Grenada also remained nominally, Elizabeth II.

If you're wondering how it's relevant: the titles can end up separating again. The most straightforward way is if the territories have different rules for who inherits the crown on death.

No I believe we have a "rule of recognition" where our monarch is just whoever the UK's monarch is.

The last time the succession rules were changed (2013), it was following an agreement by the relevant countries. It was called the "Perth Agreement".

King Charles the fourth? https://en.wikipedia.org/wiki/Charles_XV: “Charles XV […] was King of Sweden and Norway, there often referred to as Charles IV”

    assert(king_of_canada === king_of_england);

Which King Charles? The one with his head or the one without?

Since 1984. One of the facts I learned for the Canadian citizenship exam.

So only Elizabeth and Charles.

Right?! Listen, I know this sounds like a conspiracy… but I think the monarchy has historically been a mechanism used to centralize tremendous global power under a single banner. We ought to be mindful of that and, perhaps, construct checks and balances against this concentrated power.